Tropical Storm Gilma Forecast Discussion

000
WTPZ42 KNHC 210234
TCDEP2

Tropical Storm Gilma Discussion Number  11
NWS National Hurricane Center Miami FL       EP072024
800 PM PDT Tue Aug 20 2024

Gilma is holding steady this evening.  The low-level circulation is 
still hidden beneath a modest Central Dense Overcast (CDO).  Recent 
satellite microwave imagery showed the deep convection is limited to 
the southern half of the storm, with a band extending to the 
southwest of the center.  The initial intensity is held at 60 kt in 
deference to the earlier ASCAT data, slightly above the subjective 
Dvorak estimates of 55 kt from TAFB and SAB.

A ridge centered over the southwestern U.S. is steering the storm at 
an estimated 275/9 kt.  A westward to west-northwestward motion 
should continue for the next day or so.  By Thursday, a slight turn 
poleward and decrease of forward speed is expected as a deep-layer 
trough moving in from the west erodes the ridge.  Once again, the 
track model guidance has shifted southward this cycle.  The latest 
NHC track forecast has been nudged to the south and lies between the 
previous track forecast and the simple consensus aid TVCE.

Gilma seems to be holding its own against the moderate northeasterly 
wind shear.  Global models suggest the upper-level winds should 
gradually become more favorable over the next day or so, allowing 
Gilma to reach hurricane status overnight or Wednesday morning.  The 
storm should have the necessary ingredients to steadily strengthen 
through Thursday, and the forecast peak remains at 90 kt. By the end 
of the week and into the weekend, Gilma should encounter cooling sea 
surface temperatures, increasing shear, and dry mid-level humidities 
causing it to gradually weaken. The latest official forecast is 
largely an update of the previous prediction.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 16.1N 121.5W   60 KT  70 MPH
 12H  21/1200Z 16.2N 122.6W   65 KT  75 MPH
 24H  22/0000Z 16.6N 123.9W   70 KT  80 MPH
 36H  22/1200Z 17.0N 125.0W   80 KT  90 MPH
 48H  23/0000Z 17.4N 126.1W   85 KT 100 MPH
 60H  23/1200Z 17.8N 127.3W   90 KT 105 MPH
 72H  24/0000Z 18.2N 128.6W   85 KT 100 MPH
 96H  25/0000Z 18.8N 131.6W   70 KT  80 MPH
120H  26/0000Z 19.6N 135.4W   55 KT  65 MPH

$$
Forecaster Bucci